Micro Nano Devices & Systems Lab

Projects > Thermal Transport in 1-D and 2-D Nanostructures 

Thermal transport at the interfaces of low-dimensional nano-structures such as carbon nanotube (CNT) and graphene become very important in their nano-electronic devices. Accurate description of the thermal transport at nano-structure interfaces is a challenging task because the Fourier law of heat conduction begins to fail at micro/nano scales. Phonons are primary heat carriers in CNTs and graphene; a fundamental understanding of phonon transport in these nano-structures and their interfaces is needed for the energy efficient design of their devices. Atomistic scale studies of thermal transport are required to capture the physics of phonon transport at nano-structure interfaces. In this work, we focus on developing atomistic models based on molecular dynamics (MD) simulations, atomistic Green’s function (AGF) method, and density functional theory (DFT) to determine the thermal properties of carbon nano-structures interacting with various materials such as silicon oxide and metals. This study requires knowledge from multiple disciplines such as thermal science, electrical engineering, and physics.

Heat Dissipation in Nanotubes Networks on Silicon Oxide Substrate

In CNT network based transistors and MWNTs based interconnects, various CNT interfaces are involved, e.g., interlayer interfaces in DWNTs, CNT-CNT junctions, and CNT-substrate interfaces. Those interfaces are weakly coupled which makes the interfacial heat exchange very low, and the self-heating effects can significantly degrade the device performance. In this work, the thermal transport in DWNTs and CNT junctions is studied using MD simulations, and heat dissipations are analyzed in frequency domain using wavelet method and spectral temperature relaxation method. Our findings enhance the understanding of phonon coupling at CNT interfaces, identify the crucial heat transfer process from the heat dissipation at various CNT interfaces, and demonstrate the effects of substrate on thermal boundary conductance.


(a) CNT network thin film transistor. (b) Heat dissipation in CNT junctions on SiO2. (c) Heat propagation in double-wall nanotubes and (d) the corresponding wavelet transform of heat pulse

Relevant Publications
1. Liang Chen and Satish Kumar. “Heat Dissipation Mechanism at Carbon Nanotube Junctions on Silicon Oxide”. ASME Journal of Heat Transfer 2013, available online [PDF]
2. Liang Chen and Satish Kumar. “Thermal Transport in Double Wall Carbon Nanotubes Using Heat Pulse”. Journal of Applied Physics, 110(7), 074305, 2011 [PDF]

 

Phonon Coupling and Thermal Transport at Graphene/Metal Interfaces


(a) Electronic Structures at Interfaces between graphene and Cu, Au, and Ti. (b) Thermal boundary conductance variations as a function of number of graphene layer in metal/MLG/metal. Inset shows the phonon transmission and scattering mechanism.

Single layer graphene (SLG) and multi-layer graphene (MLG) is a promising semiconductor material for nano-electronic devices due to the high carrier mobility, high thermal conductivity, and tunable band gap. Low thermal boundary conductance (TBC) at graphene-metal interface can become a critical challenge for high frequency applications of graphene based devices. It is of practical importance to predict TBC, and decipher phonon transport mechanism at various graphene/metal interfaces to engineer these interfaces for effective thermal management and enhanced performance. In this work, we use density functional theory calculations to determine interfacial bonding, and perform AGF and MD simulations to study the effects of bonding on various thermal properties, e.g. thermal conductivity of graphene and phonon transmission and TBC at graphene/metal interfaces.

 

 

 

 

 

 

Relevant Publications
1. Liang Chen, Zhen Huang, and Satish Kumar. “Impact of Interfacial Bonding on Thermal Boundary Conductance between Multi-layer Graphene and Metal”, manuscript submitted
2. Liang Chen, Zhen Huang, and Satish Kumar. “Phonon Transmission and Thermal Conductance across Graphene/Cu Interface”. Applied Physics Letters 103(12), 4821439, 2013 [PDF]
3. Liang Chen and Satish Kumar. “Thermal Transport in Graphene Supported on Copper”. Journal of Applied Physics 112(4), 043502, 2012 [PDF]

 

Funding: NSF